Impacts of the Minimum Legal Drinking Age on Motor Vehicle Collisions in Québec, 20002012 Russell C. Callaghan, PhD, Jodi M. Gatley, BSc, Marcos Sanches, MSc, Mark Asbridge, PhD Background: International debates are occurring about the effectiveness of minimum legal drinking age laws. Most minimum legal drinking age evaluation studies have focused on motor vehicle collision outcomes, but this literature is primarily based on naturalistic experiments involving legislation changes in the U.S. in the mid-1980s. Few studies have provided up-to-date estimates of the impacts of Canadian drinking age laws on motor vehicle collisions to inform current policy discussions. Purpose: To estimate the impacts of minimum legal drinking age legislation on motor vehicle collisions occurring in 2000–2012 in Québec, a province with a minimum legal drinking age of 18 years. Methods: Using Québec Ministry of Transportation records of police-reported motor vehicle collisions in 20002012, regression-discontinuity analyses were employed to assess the impacts of the minimum legal drinking age on motor vehicle collisions. All data were analyzed in 2013.
Results: Relative to individuals slightly younger than the minimum legal drinking age, male and female drivers just older than the minimum legal drinking age had a significant and abrupt increase of approximately 6% (men, 6.3%, p¼0.003; women, 5.9%, p¼0.047) in population-level motor vehicle collisions, as well as a significant 11.1% (p¼0.001) rise in nighttime motor vehicle collisions (a proxy for alcohol-related collisions). Conclusions: Drinking-age laws continue to be an integral component of contemporary alcoholcontrol and driving-related policies designed to limit motor vehicle collisions among youth. In addition, the regression-discontinuity approach can guide future work to estimate potential minimum legal drinking age impacts on other health outcomes. (Am J Prev Med 2014;47(6):788–795) & 2014 American Journal of Preventive Medicine
Introduction
A
lcohol use is the largest contributor to the global burden of morbidity and mortality among adolescents and young adults.1,2 For many decades, countries worldwide have implemented minimum legal From the Northern Medical Program (Callaghan, Gatley), University of Northern British Columbia, Prince George, British Columbia; Human Brain Laboratory (Callaghan, Gatley), Centre for Addiction and Mental Health, Dalla Lana School of Public Health (Callaghan), University of Toronto; Biostatistical Consulting Unit (Sanches), Centre for Addiction and Mental Health, Toronto, Ontario; and the Department of Community Health and Epidemiology (Asbridge), Dalhousie University, Halifax, Nova Scotia, Canada Address correspondence to: Russell C. Callaghan, PhD, University of Northern British Columbia, Northern Medical Program, 3333 University Way, V2N 4Z9, Prince George British Columbia, Canada. E-mail: russ. [email protected]. 0749-3797/$36.00 http://dx.doi.org/10.1016/j.amepre.2014.08.012
788 Am J Prev Med 2014;47(6):788–795
drinking age (MLDA) legislation in order to reduce alcohol-related harms among young people.3 In the Canadian context, the MLDA is under provincial jurisdiction, and almost all provinces set their current legislated drinking ages in the mid-to-late 1970s. The MLDA is 18 years in Alberta, Manitoba, and Québec, and 19 years in the remainder of Canada. Recently, the Canadian Public Health Association4 and the Canadian National Alcohol Strategy working group5 have recommended raising the MLDA across all provinces to 19 years. In 2013, an expert panel alcohol-policy coalition identified a national MLDA of 21 years as the ideal,6 and province-specific recommendations have been released for all provinces (except Québec),7–15 endorsing an increase in the MLDA to 21 years. At their 2012 annual convention, the members of the Saskatchewan Party (the province’s conservative party) voted to lower the MLDA to 18 years, but this platform was later rejected by the
& 2014 American Journal of Preventive Medicine
Published by Elsevier Inc.
789
Callaghan et al / Am J Prev Med 2014;47(6):788–795 16
government. These Canadian MLDA discussions are occurring against broader movements in some jurisdictions to “modernize” alcohol policies so as to liberalize liquor access, shift to greater privatization of alcohol sales (away from a government monopoly model), and increase alcohol sales in the population.17–19 Current MLDA debates usually focus on a calculus of harms/benefits associated with proposed legislative changes, and motor vehicle collisions (MVCs) stand as one of the more prominent outcomes measured to assess the effectiveness of MLDA legislation. However, providing up-to-date estimates of the impacts of the MLDA on current patterns of MVCs represents a significant methodologic challenge. Most available studies assessing the impacts of MLDA legislation on MVCs have relied on naturalistic experiments occurring in the U.S. in the mid1980s,20 with few studies from other countries (e.g., New Zealand)21 or projects using data from other time periods. In general, the literature on the effects of MLDA changes on fatal/nonfatal MVCs in youth populations has found that raising the MLDA was associated with decreases, and lowering the MLDA was associated with increases.20,22–28 Many of these studies, however, are decades old and it would be reasonable to argue that the impacts of MLDA observed in the 1970s and 1980s might be substantially attenuated in the contemporary context, owing in large part to advances in both traffic safety and alcohol policy (e.g., road and vehicle safety,29,30 graduated driver licensing legislation,31–34 and impaired-driving laws35–37). This study makes an important contribution to Canadian4,6–8,16 and international38–41 (e.g., theamethys tinitiative.org/) MLDA debates by providing current estimates of MLDA effectiveness and demonstrating the use of a quasi-experimental statistical approach— regression-discontinuity (RD) analysis—for examining MLDA impacts on MVCs. RD analyses have been used previously to examine the impacts of U.S. MLDA laws on mortality42,43 and consumption of alcohol, cannabis, and tobacco.44,45 An RD approach does not rely on the occurrence of acute policy changes (i.e., natural experiments) to assess the impact of MLDA legislation on MVCs. The guiding hypothesis is that young adults slightly older than the MLDA would have significantly elevated collision patterns in comparison to those individuals still under the MLDA restrictions.
Methods Data Source De-identified data were obtained on police-reported MVCs occurring in Québec from January 1, 2000December 31, 2012 involving drivers aged 17.518.5 years from the Société de l'assurance automobile du Québec (SAAQ). The SAAQ is the sole December 2014
government insurer and insures against personal injury, while other private insurers provide coverage for property damage.46 The SAAQ MVC database captures all MVCs in the province reported to the SAAQ provincial insurance agency by the Québec police. Attending Québec police must report all collisions in the province to SAAQ in which a person sustained an injury. For MVCs causing property damage only, police must report to SAAQ all collisions in Québec if the property damage was estimated to be in excess of $1,000 before March 18, 2010 or $2,000 after that date. Off-road collisions (involving vehicles operating outside the Municipal, Provincial, or Federal road systems) are not included in the database. It is not possible to estimate the number of collisions unreported to SAAQ.
Analytic Plan An RD design47,48 was employed—a quasi-experimental approach that can provide credible estimates of the causal effect of an intervention on a specified outcome.49 The RD design takes advantage of the sharp discontinuity in the legality of alcohol purchasing and consumption appearing at the MLDA; this study’s approach assigns participants younger than the MLDA to the “alcohol-restricted” group and young adults no longer subject to the MLDA to the “alcohol-accessible” group. The primary, intuitive idea of the RD approach is that individuals slightly older and those slightly younger than the MLDA will be similar in observed (and unobserved) characteristics, except for the influence of the removal of the MLDA in the “alcohol-accessible” group. The RD design assumes that all observed and unobserved variables (which might influence the alcohol-related outcomes) are smoothly distributed across the age cutoff,50 and the effects of the MLDA can be inferred if the regression line shows a discontinuity—a change in intercept—at the MLDA.51 In other words, as the observed and unobserved determinants of the MVC outcomes (other than the legal granting of access to alcohol) are likely to be distributed smoothly across the MLDA threshold, any abrupt increases in the outcome rates immediately after the MLDA can be reasonably attributed to legal availability of alcohol. Additionally, a major advantage of the RD approach is that the results can be visually represented in easy-to-understand scatterplots. The mathematical formula (Equation 1) for the RD analyses is: P
Y¼ αþ β1 MLDAþ β2 Birth þ ∑ ðγk Agek þ λk Agek MLDAÞþ ε; k¼1
where the term Y is the number of MVCs; MLDA is the indicator of whether a driver’s age is above the MLDA of 18 years, and its coefficient β1 is the estimate of the MLDA effect; Birth is the indicator of birthday week (which accommodates “birthday celebration” effects occurring at the MLDA); Birth was coded as “1,” if the police-reported collision occurred during the individual’s birthday week), “0” for all other weeks; Age (in weeks) is a running variable, centered at the MLDA, with p¼1,2,3 representing the degree of the polynomial equation across Age, which includes the MLDAAge interaction term (the interaction allows for different regression equations before and after the MLDA cutoff); α is the intercept, which is the estimate of the baseline number of MVCs (i.e., the number of MVCs just before the legislated MLDA); and ε is the error term. The RD approach followed the recent best-practice guidelines for RD analyses.51 Parametric regression analyses were conducted, including linear, quadratic, and cubic models. Regarding selection
790
Callaghan et al / Am J Prev Med 2014;47(6):788–795
of the “best” model, the cubic model was chosen when the cubic term for age in Equation 1 was statistically significant; the quadratic model when the quadratic term for age was statistically significant (but not the cubic term); and a linear model when neither the cubic nor the quadratic term were statistically significant. In other words, the quadratic and cubic terms were tested in each full RD model, and then dropped from the final models if not statistically significant. The selection algorithm for the best model followed the standard rationale for model selection in regression analyses.52,53 Also, prior studies by this research team54–56 found significant gender-by-MLDA or gender-by-age interaction effects in all RD models—patterns that provide statistical justification for conducting gender-specific analyses. Sensitivity RD models were also run using Poisson regression, and these results confirmed our final findings (which were based on linear models). The RD models worked on aggregated MVC counts across age. Therefore, this approach does not follow individuals over time, but rather assesses population-based counts of driver involvement in MVCs across age groupings of age in weeks leading up to and after the MLDA across the data span. The R statistical package (“lm” and “glm”), version 2.15.3 was used to conduct the analyses. All data analyses were performed in 2013.
Results
Number of Drivers Involved in Collisions
Trends (centered at the MLDA) in the total number of MVCs for the combined sample, as well as for male and female drivers separately, can be found in Figure 1. Figure 1 demonstrates a significant and abrupt increase in MVCs occurring among youth slightly older than the MLDA for the total sample and male and female youth. Trends in the number of single-vehicle nighttime MVCs for the combined sample, as well as for male and female participants, can be found in Figure 2. The magnitude of the jumps at the MLDA can be found in the row “Effect (%)” in Tables 1 and 2. Among female youth, there was no evidence of a statistically significant increase in single-vehicle nighttime MVCs immediately after the MLDA. Among male youth, female youth, and the total sample, there was evidence of significant increases in all MVCs appearing immediately after the MLDA, with more pronounced “jumps” among male in comparison with female drivers. Tables 1 and 2 present key parameter results from linear RD models, which were the “best” fitting in all of the RD analyses (estimates for all RD parameters across Construction of Motor Vehicle Collision Outcomes all models [i.e., linear, quadratic, and cubic] are available from the primary author). Significant “jumps” were The SAAQ database does not include a variable indicating whether observed in total MVCs of 6.2% for the combined sample the MVC was alcohol-related. Therefore, the following proxies were used to identify alcohol-related MVCs: (1) nighttime MVCs (pr0.001), as well as for male (6.3%, p=0.003) and from the hours of 10:00PM to 6:59AM and (2) single-vehicle female (5.9%, p=0.047) youth (Figure 1). The number of nighttime MVCs. MVCs occurring at night are commonly used nighttime MVCs increased by 11.1% immediately after as a surrogate to identify alcohol-related collisions.3,36,57 Two the MLDA in the combined sample (p¼0.001), and thirds of fatal nighttime MVCs involve alcohol, compared with one increased by 9.5% among male drivers (p¼0.010). The quarter of daytime MVCs.43 number of daytime MVCs 1,600 increased by 5% among the Minimum legal drinking age combined sample (p¼0.003) 1,400 and by 5.5% among male youth (p¼0.012). The num1,200 ber of single-vehicle nighttime MVCs increased 9.3% Total for the total sample 1,000 (p¼0.006) and 8.7% among Female male drivers (p¼0.990) 800 Male (Figure 2). There were also nonsignificant increases 600 among female drivers of 16.3% in the number of 400 nighttime MVCs (p¼0.060), 4.2% in the number of day200 time MVCs (p¼0.191), and 13.1% in the number of 0 single-vehicle nighttime 18.5 18 17.5 MVCs (p¼0.328) (Figure 2). Drivers' Age in Years Visual and statistical tests (BreuschPagan) were perFigure 1. Police-reported motor vehicle collisions among individuals aged 17.518.5 formed on the presented final years in Québec, 20002012. www.ajpmonline.org
791
Callaghan et al / Am J Prev Med 2014;47(6):788–795
MVCs were evaluated at ages 17 and 19 years, and there was no evidence of statistically significant discontinuities (data not shown, available from first author).
180 Number of Drivers Involved in Collisions
Minimum legal drinking age 160 140 120 100
Total Female
Discussion
MLDA legislation has a powerful impact on MVCs among 60 young drivers in Québec, Canada. In comparison to youth just 40 younger than the MLDA, male and female youth just older than 20 the MLDA had a significant increase of approximately 6% 0 in population-level MVCs, as 17.5 18 18.5 well as an 11% increase in the Drivers' Age in Years number of nighttime MVCs. Granting that the major assumpFigure 2. Police-reported single-vehicle nighttime (10:00PM to 6:59AM) motor vehicle tions of the analytic approach collisions among individuals aged 17.518.5 years in Québec, 20002012. (RD) were met, this study can RD models to ensure homoscedasticity of variance in the provide credible population-based estimates of the causal residuals. No violations appeared. RD models using impact of granting legal access to alcohol on the number Poisson regression showed results similar to the final of MVCs among young people in Québec. presented models (data not shown). The estimates of the impacts of the MLDA on MVCs Based on these results, estimates were also made that dovetail with findings from the existing, albeit older, raising the MLDA to 19 years in Québec would reduce MLDA literature, which is primarily from the U.S. the number of MVCs involving at least one 18-year-old Raising the U.S. MLDA to 21 years (from ages 18 or 19 driver by 6.2%, resulting in 4,376 fewer collisions years, depending on jurisdiction) was associated with (6.2% 70,585 MVCs involving at least one 18-year-old decreases (1%8%58 and 8%17%22) in alcohol-related driver) from 2000 to 2012. It was estimated that raising fatal/nonfatal MVCs among drivers aged 1820 years, the MLDA to 19 years would result in approximately 337 and an 11% decrease in the proportion of alcohol-related fewer collisions per year (4,376 total collisions/13-year fatal MVCs for the whole population59; lowering of the data span) involving at least one 18-year-old driver in MLDA was associated with an increase in the total Québec. Assuming a reduction of the MLDA effect by number of fatal MVCs among 18- to 21-year-olds by half for each year of age after 18 years (i.e., 6.2% for 187%9% (Carpenter C, Dobkin C. The effects of the year-olds, 3.1% for 19-year-olds, and 1.55% for 20-yearminimum legal drinking age on morbidity, unpublished olds), it could be expected that such a policy would result observations, 2011).24 In relation to nighttime/singlein approximately 7,578 fewer MVCs during the 13-year vehicle nighttime MVCs, evidence suggests that lowering study period (6.2% 70,585 ¼ 4376 MVCs involving at the MLDA from 21 to 18 years was associated with a 17% least one 18-year-old driver, 3.1% 70,006 ¼ 2,170 increase in fatal nighttime (8:00PM to 5:59AM) MVCs MVCs involving at least one 19-year-old driver, and among 18- to 20-year-olds (Carpenter C, Dobkin C. The 1.55% 66,597 ¼ 1032 MVCs involving at least one 20effects of the minimum legal drinking age on morbidity, year-old driver, 4376 þ 2170 þ 1032 ¼ 7,578). If the unpublished observations, 2011). As a result, this study MLDA were raised to 21 years in Québec, it was not only shows the usefulness of the RD approach for estimated that this would prevent approximately 583 recovering reasonable estimates of the impacts of MLDA police-reported MVCs per year involving at least one legislation, but also demonstrates the continuing effecdriver aged between 18 and 20 years. tiveness of MLDA laws as an integral component in the 51 Guidelines for the use of RD analyses suggest testing contemporary array of alcohol-control and drivingfor jumps at nearby nondiscontinuity points before and related policies designed to reduce MVCs among youth after the specified forcing variable (the MLDA). Jumps in in the population. 80
December 2014
Male
792
0.1900 0.0119
4.2 (2.1, 10.5) 5.5 (1.3, 9.7)
Note: Boldface indicates statistical significance (po0.05). a The Québec MLDA is 18 years of age. b Percentage change in MVC events at the MLDA threshold (the coefficient of the MLDA indicator divided by the intercept of the model). MLDA, minimum legal drinking age; MVC, motor vehicle collision; RD, regression-discontinuity.
0.0034 0.0473 0.0031 MLDA effect, p-value
0.0004
5.9 (0.1, 11.8) Effect (%)
6.2 (2.9, 9.4)
6.3 (2.2, 10.4)
5 (1.8, 8.3)
0.9 (2.5, 0.6) 0.7 (2.5, 1.1) 0.6 (2.3, 1.1)
b
Age MLDA
1.7 (4.4, 1.1)
1.1 (3.3, 1.2)
1.7 (3.9, 0.6)
25.3 (70.1, 19.4) 1.6 (50.1, 53.3) 33.7 (82.2, 14.8) Birthday week
52.2 (129.6, 25.3)
16.9 (80.3, 46.5)
25 (88.6, 38.6)
15.8 (8.1, 39.6) 35.9 (8.3, 63.4) 26.2 (0.3, 52.1) MLDA
78.7 (37.4, 120.1)
52.46 (18.6, 86.3)
52.1 (18.1, 86.0)
0.8 (0.3, 1.8) 1.6 (0.4, 2.9) 0.7 (0.5, 1.9)
2.4 (0.9, 3.9)
Although the results of this study cannot directly answer the counterfactual question—How many MVCs would be prevented if the Québec MLDA were raised to 19 years?—these findings can provide a reasonable estimate. It was estimated that raising the Québec MLDA to 19 years would prevent 337 police-reported collisions per year involving at least one 18-year-old driver in the province. If the MLDA were to be raised to 21 years, it could be expected that this legislation would result in the prevention of approximately 583 police-reported MVCs per year involving at least one driver aged between 18 and 20 years.
Legislative Changes Related to Driving in Québec, 20002012
2.64 (1.1, 4.2) 3.3 (1.5, 5.2) Age
377.6 (360.9, 394.3) 652.5 (633.2, 671.8) 441.5 (423.4, 459.6) Intercept
1272.4 (1243.5, 1301.3)
828.4 (804.7, 852.1)
1032 (1008.2, 1055.7)
Female (95% CI) Male (95% CI) Total (95% CI) Female (95% CI) Male (95% CI) Total (95% CI) Model parameters
All MVCs
Table 1. RD parameters: drivers involved in all and daytime MVCs following the Québec MLDAa, 20002012
Daytime MVCs (7:00AM9:59PM)
Callaghan et al / Am J Prev Med 2014;47(6):788–795
During the span of this study, several pieces of legislation affecting young/new drivers were enacted in Québec, however, it is unlikely that any of these would have impacted our estimates. The following laws were implemented in Québec between 2000 and 2012: harsher penalties for impaired driving and speeding (April and December 2008),60 mandatory completion of an approved Road Safety Education Program to obtain a learner’s license (January 17, 2010),61 a graduated demerit point scale for drivers younger than age 25 years (June 19, 2011),62 and a zero-tolerance blood alcohol concentration law was introduced for drivers aged r21 years and for those drivers with a learner’s or probationary license (April 15, 2012),63 It was not expected that these changes would confound the estimates of the impacts of the MLDA legislation on MVCs because the legislation did not differentially affect those drivers slightly younger and those just older than the MLDA of 18 years.
Limitations The findings of the current study must be interpreted in light of a number of limitations. The analytic strategy employed an RD approach, which assumes that potentially confounding variables are smoothly distributed across the MLDA cutoff. If a factor differentially affected individuals on either side of the MLDA, then this would undermine the validity of the estimates. In Québec, there is a major educational transition from high school to a 2- or 3-year post-secondary Collège d'enseignement général et professionnel (CÉGEP) program, typically entered at age 17 years.64,65 In the analyses, drivers aged 17.518.5 years were included. This span does not overlap with major transitions into or out of the CÉGEP system, limiting the possibility that educational transitions may have affected the outcomes. In addition, the outcomes only included police-reported MVCs in www.ajpmonline.org
December 2014
Note: Boldface indicated statistical significance (po0.05). a The Québec MLDA is 18 years of age. b Percentage change in MVC events at the MLDA threshold (the coefficient of the MLDA indicator divided by the intercept of the model). MLDA, minimum legal drinking age; MVC, motor vehicle collision; RD, regression-discontinuity.
0.3300 0.9900 0.0600 MLDA effect, p-value
0.0013
0.0102
0.0060
13.1 (13.2, 39.4) 8.7 (11.8, 11.9) 16.3 (1.7, 34.3) 9.5 (2.2, 16.7) Effect (%)
11.1 (4.3, 17.7)
9.3 (2.7, 16.0)
0.7 (0.2, 1.1) 0.1 (0.8, 0.6) 0.3 (0.4, 1.1) 0.4 (1.2, 0.5)
b
Age MLDA
0.0 (1.0, 1.0)
0.5 (0.2, 1.2)
3.3 (9.2, 15.7) 2.5 (16.2, 21.3) 8.4 (28.8, 12.1) 18.5 (41.9, 4.9) Birthday week
27.1 (56.4, 2.2)
5.7 (14.0, 25.3)
3.5 (3.2, 10.1) 7.5 (2.5, 17.5) 10.4 (0.5, 21.3) 16.6 (4.1, 29.1) MLDA
26.7 (11.0, 42.3)
10.5 (0.1, 21.0)
0.3 (0.6, 0.0) 0.5 (0.0, 0.9) 0.1 (0.6, 0.4) Age
0.9 (0.2, 1.7)
1 (0.4, 1.6)
0.2 (0.3, 0.7)
26.3 (21.6, 30.9) 86 (79.0, 93.0) 63.9 (56.3, 71.6) 175.9 (167.1, 184.6) Intercept
240.5 (229.5, 251.4)
112.8 (105.5, 120.1)
Female (95% CI) Male (95% CI) Total (95% CI) Female (95% CI) Male (95% CI) Total (95% CI) Model parameters
Single-vehicle nighttime MVCs (10:00PM to 6:59AM) Nighttime MVCs (10:00PM to 6:59AM)
Table 2. RD parameters: drivers involved in nighttime and single-vehicle nighttime MVCs following the Québec MLDA,a 20002012
Callaghan et al / Am J Prev Med 2014;47(6):788–795
793
Québec, and it was not possible to estimate the number of unreported MVCs during the data span. Nonetheless, if alcohol-related MVCs are more likely to go unreported than other MVCs, then the estimates of the impacts of the MLDA MVCs using SAAQ data would be conservative. Unfortunately, the data did not include information about driving experience (or age of initial licensing). However, it is reasonable to expect that older individuals included in the analyses would have more driving experience. If increased driving experience in this population confers a reduced risk of MVC, it is likely that the estimated effect of the MLDA is conservative, given the findings of elevated MVC patterns in the moreexperienced young drivers in the post-MLDA age group. Also, in calculations of the potential MVCs prevented if the MLDA were in Québec, it was assumed that there would be a 50% reduction in the demonstrated effect of the MLDA for each year of age after 18 years (i.e., 6.2% for 18-year-olds, 3.1% for 19-year-olds, and 1.55% for 20year-olds). The actual impacts of the MLDA on 19- to 20year-olds may be different.
Conclusions Given the very recent recommendations to raise the Canadian MLDA to 19 years (or to 21 years in some provinces), it is critical for Canadian alcohol policy debates to have current estimates of the impacts of the MLDA on MVCs—a key public health outcome. The available Canadian research on the effects of the MLDA on MVCs was published from the period from 1975 to 1981 and, therefore, this study provides important up-todate information demonstrating that MLDA legislation continues to have a significant impact on MVCs among male and female youth. The authors would like to thank Julie Béliveau (Statistician [Direction des études et des stratégies en sécurité routière, Société de l'assurance automobile du Québec]) for her assistance in helping us to acquire the Québec collision database and understand its structure. The current study was supported through internal startup funds from the Northern Medical Program (University of Northern British Columbia) to the first author (RCC). No financial disclosures were reported by the authors of this paper.
References 1. Gore FM, Bloem PJ, Patton GC, et al. Global burden of disease in young people aged 1024 years: a systematic analysis. Lancet 2011; 377(9783):2093–102. 2. Lim SS, Vos T, Flaxman AD, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk
794
3. 4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18. 19.
Callaghan et al / Am J Prev Med 2014;47(6):788–795
factor clusters in 21 regions, 19902010: a systematic analysis for the global burden of disease study 2010. Lancet 2012;380(9859):2224–60. Babor T, Caetano R, Casswell S, et al. Alcohol: no ordinary commodity. 2nd ed. New York NY: Oxford University Press, 2010. Canadian Public Health Association. Canadian Public Health Association position paper: too high a cost: a public health approach to alcohol policy in Canada. Ottawa ON: Canadian Public Health Association, 2011 www.cpha.ca/uploads/positions/position-paper-alco hol_e.pdf. Sawka E, Liepold H, Lockhart N, Song S, Thomas G. Reducing alcoholrelated harm in Canada: toward a culture of moderation. Recommendations for a national alcohol strategy. Ottawa ON: Canadian Centre on Substance Abuse, 2007 www.ndphs.org///documents/515/Canada_ Paper_NAS_to_Riga_Conference_Jan_30_07_1.pdf. Giesbrecht N, Wettlaufer A, April N, Asbridge M, et al. Strategies to reduce alcohol-related harms and costs in Canada: a comparison of provincial policies. Toronto ON: Centre for Addiction and Mental Health, 2013. www.camh.ca/en/research/news_and_publications/reports_and_ books/Documents/Strategies%20to%20Reduce%20Alcohol%20Related% 20Harms%20and%20Costs%202013.pdf. Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Ontario: a provincial summary report. Toronto ON: Centre for Addiction and Mental Health, 2013 www.camh.ca/en/research/Docu ments/Provincial%20summary_ON_final.pdf. Thompson K, Stockwell T, Vallance K, Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in British Columbia: a provincial summary report. CARBC Bulletin #10. Victoria BC: Centre for Addictions Research of British Columbia, 2013 www.carbc.ca/ Portals/0/propertyagent/558/files/335/bulletin%202013-08.pdf. Vallance K, Thompson K, Stockwell T, Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Alberta: a provincial summary report. Victoria BC: Centre for Addictions Research of BC, 2013. www.carbc.ca/Portals/0/propertyagent/558/files/352/albertaprov summ2013-09.pdf. Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Manitoba: a provincial summary report. Toronto ON: Centre for Addiction and Mental Health, 2013. Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Saskatchewan: a provincial summary report. Toronto ON: Centre for Addiction and Mental Health, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in New Brunswick: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in Newfoundland and Labrador: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in Nova Scotia: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in Prince Edward Island: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. CBC News. Drinking age will remain 19 in Saskatchewan. CBC News. 2013. www.cbc.ca/news/canada/saskatchewan/story/2013/03/04/skdrinking-age-1303.html. British Columbia Ministry of Justice. B.C. liquor policy review final report. Victoria BC: British Columbia Ministry of Justice, 2013. www2. gov.bc.ca/local/haveyoursay/Docs/liquor_policy_review_report.pdf. Government of Saskatchewan. Liquor regulatory review—additional information. Regina SK: Government of Saskatchewan, 2013. Liquor and Gaming Regulatory Consultation Committee. A discussion paper on liquor and gaming regulation. Winnipeg MB: Manitoba Gaming Control Commission, 2012.
20. Wagenaar AC, Toomey TL. Effects of minimum drinking age laws: review and analyses of the literature from 1960 to 2000. J Stud Alcohol Suppl 2002;14:206–25. 21. Kypri K, Voas RB, Langley JD, et al. Minimum purchasing age for alcohol and traffic crash injuries among 15- to 19-year-olds in New Zealand. Am J Public Health 2006;96(1):126–31. 22. Shults RA, Elder RW, Sleet DA, et al. Reviews of evidence regarding interventions to reduce alcohol-impaired driving. Am J Prev Med 2001;21(4S):66–88. 23. McCartt AT, Hellinga LA, Kirley BB. The effects of minimum legal drinking age 21 laws on alcohol-related driving in the United States. J Safety Res 2010;41(2):173–81. 24. Cook PJ. Paying the tab: the costs and benefits of alcohol control. Princeton NJ: Princeton University Press, 2007. 25. Fell JC, Fisher DA, Voas RB, Blackman K, Tippetts AS. The impact of underage drinking laws on alcohol-related fatal crashes of young drivers. Alcohol Clin Exp Res 2009;33(7):1208–19. 26. Fell JC, Fisher DA, Voas RB, Blackman K, Tippetts AS. The relationship of underage drinking laws to reductions in drinking drivers in fatal crashes in the United States. Accid Anal Prev 2008;40(4):1430–40. 27. Voas RB, Tippetts AS, Fell JC. Assessing the effectiveness of minimum legal drinking age and zero tolerance laws in the United States. Accid Anal Prev 2003;35(4):579–87. 28. Ponicki WR, Gruenewald PJ, LaScala EA. Joint impacts of minimum legal drinking age and beer taxes on US youth traffic fatalities, 1975 to 2001. Alcohol Clin Exp Res 2007;31(5):804–13. 29. Kahane CJ. Lives saved by the federal motor vehicle safety standards and other vehicle safety technologies, 1960-2002—passenger cars and light trucks—with a review of 19 FMVSS and their effectiveness in reducing fatalities, injuries and crashes. Washington DC: Evaluation Division, National Center for Statistics and Analysis National Highway Traffic Safety Administration, 2004. 30. Waller PF. Challenges in motor vehicle safety. Annu Rev Publ Health 2002;23:93–113. 31. Dee TS, Grabowski DC, Morrisey MA. Graduated driver licensing and teen traffic fatalities. J Health Econ 2005;24(3):571–89. 32. McCartt AT, Teoh ER, Fields M, Braitman KA, Hellinga LA. Graduated licensing laws and fatal crashes of teenage drivers: a national study. Traffic Inj Prev 2010;11(3):240–8. 33. Masten SV, Foss RD, Marshall SW. Graduated driver licensing and fatal crashes involving 16- to 19-year-old drivers. JAMA 2011;306(10): 1098–103. 34. Mayhew DR, Simpson HM, Singhal D. Best practices for graduated driver licensing in Canada. Ottawa ON: Traffic Injury Research Foundation, 2005 www.ibc.ca/en/Car_Insurance/documents/gradua ted_licensing/TIRF-fullreportGDL-oct2005.pdf. 35. Asbridge M, Mann RE, Smart RG, et al. The effects of Ontario’s administrative driver's license suspension law on total driver fatalities: a multiple time series analysis. Drugs Educ Prev Policy 2009;16(2): 140–51. 36. Mann RE, Macdonald S, Stoduto G, Bondy S, Jonah B, Shaikh A. The effects of introducing or lowering legal per se blood alcohol limits for driving: an international review. Accid Anal Prev 2001;33(5):569–83. 37. Vingilis E, Blefgen H, Lei H, Sykora K, Mann R. An evaluation of the deterrent impact of Ontario’s 12-hour license suspension law. Accid Anal Prev 1988;20(1):9–17. 38. Cobiac L, Vos T, Doran C, Wallace A. Cost-effectiveness of interventions to prevent alcohol-related disease and injury in Australia. Addiction 2009;104(10):1646–55. 39. Doran CM, Hall WD, Shakeshaft AP, Vos T, Cobiac LJ. Alcohol policy reform in Australia: what can we learn from the evidence? Med J Aust 2010;192(8):468–70. 40. Manins R. Alcohol reform bill through faster. Otago NZ: Otago Daily Times, 2012 www.odt.co.nz/news/dunedin/237188/alcohol-reformbill-through-faster.
www.ajpmonline.org
Callaghan et al / Am J Prev Med 2014;47(6):788–795 41. Toomey TL, Nelson TF, Lenk KM. The age-21 minimum legal drinking age: a case study linking past and current debates. Addiction 2009;104(12):1958–65. 42. Carpenter C, Dobkin C. The effect of alcohol consumption on mortality: regression discontinuity evidence from the minimum drinking age. Am Econ J Appl Econ 2009;1(1):164–82. 43. Carpenter C, Dobkin C. The minimum legal drinking age and public health. J Econ Perspect 2011;25(2):133–56. 44. Yörük BK, Yörük CE. The impact of minimum legal drinking age laws on alcohol consumption, smoking, and marijuana use: evidence from a regression discontinuity design using exact date of birth. J Health Econ 2011;30(4):740–52. 45. Yörük CE, Yörük BK. The impact of drinking on psychological wellbeing: evidence from minimum drinking age laws in the United States. Soc Sci Med 2012;75(10):1844–54. 46. Insurance Bureau of Canada. Car insurance. http://www.ibc.ca/en/ Car_Insurance/PQ/. 47. Shadish WR, Cook TD, Campbell DT. Experimental and quasiexperimental designs for generalized causal inference. Boston MA: Houghton Mifflin Company, 2002. 48. Thistlethwaite DL, Campbell DT. Regression-discontinuity analysis: an alternative to the ex post facto experiment. J Educ Psychol 1960;51(6): 309–17. 49. Lee DS, Lemieux T. Regression discontinuity designs in economics. J Econ Lit 2009;48(2):281–355. 50. Hahn J, Todd P, Van der Klaauw W. Identification and estimation of treatment effects with a regression-discontinuity design. Econometrica 2001;69(1):201–9. 51. Imbens GW, Lemieux T. Regression discontinuity designs: a guide to practice. J Econometrics 2007;142(2):615–35. 52. Seber GA, Lee AJ. Linear regression analysis. New York NY: John Wiley & Sons Inc, 2003. 53. Freund RJ, Wilson WJ, Sa P. Regression analysis: statistical modeling of a response variable. 2nd ed. New York NY: Academic Press by Elsevier Inc, 2006. 54. Callaghan RC, Sanches M, Gatley JM, Cunningham JK. Effects of the minimum legal drinking age on alcohol-related health service use in hospital settings in Ontario: a regression-discontinuity approach. Am J Public Health 2013;103(12):2284–91.
December 2014
795
55. Callaghan RC, Sanches M, Gatley JM. Impacts of drinking-age laws on mortality in Canada, 1980–2009. Drug Alcohol Depen 2014;138: 137–45. http://dx.doi.org/10.1016/j.drugalcdep.2014.02.019. 56. Callaghan RC, Sanches M, Gatley JM. Impacts of the minimum legal drinking age legislation on in-patient morbidity in Canada, 19972007: a regression-discontinuity approach. Addiction 2013;108(9):1590–600. 57. Young DJ, Stockwell T, Cherpitel CJ, et al. Emergency room injury presentations as an indicator of alcohol-related problems in the community: a multilevel analysis of an international study. J Stud Alcohol 2004;65(5):605–12. 58. Hoskin A, Yalung-Mathews D, Carraro B. The effect of raising the legal minimum drinking age on fatal crashes in 10 states. J Safety Res 1986;17:117–21. 59. Chang K, Wu CC, Ying YH. The effectiveness of alcohol control policies on alcohol-related traffic fatalities in the United States. Accid Anal Prev 2012;45:406–15. 60. Berthod C, Audet L, Bélanger C. Table Québécoise de la sécurité routière [Quebec safety task force]. Table Québécoise de la sécurité routière [Quebec safety task force]. Presentation for “Road safety vision successor plan for 2015 and other safety plans” at the Transportation Association of Canada’s 2010 Annual Conference and Exhibition in Halifax, NS, 2010. http://conf.tac-atc.ca/english/resourcecentre/read ingroom/conference/conf2010/docs/c1/berthod-e.pdf. 61. Société de l'assurance automobile du Québec. Frequently asked questions. Mandatory driving course measures in effect as of January 17, 2010. www.saaq.gouv.qc.ca/en/faq/driving_course.php#q1. 62. Société de l'assurance automobile du Québec. Driver's licence. Penalties related to demerit points. www.saaq.gouv.qc.ca/en/driver_licence/pen alties_demerit_points.php. 63. Société de l'assurance automobile du Québec. Road safety. Zero alcohol. www.saaq.gouv.qc.ca/en/road_safety/behaviour/alcohol/laws_ penalties_costs/zero_alcohol.php. 64. Statistics Canada. Table 1. Postsecondary participation rates of young adults aged 24 to 26 by December 2005, by province and type of institution attended. Toronto ON: Statistics Canada, 2008. www. statcan.gc.ca.myaccess.library.utoronto.ca/pub/81-595–m/2008070/t/ 6000006-eng.htm. 65. Les CÉGEPS du Québec. Directory of programs. http://www.cegep squebec.ca/en/study-in-quebec/programs/.
Results: Relative to individuals slightly younger than the minimum legal drinking age, male and female drivers just older than the minimum legal drinking age had a significant and abrupt increase of approximately 6% (men, 6.3%, p¼0.003; women, 5.9%, p¼0.047) in population-level motor vehicle collisions, as well as a significant 11.1% (p¼0.001) rise in nighttime motor vehicle collisions (a proxy for alcohol-related collisions). Conclusions: Drinking-age laws continue to be an integral component of contemporary alcoholcontrol and driving-related policies designed to limit motor vehicle collisions among youth. In addition, the regression-discontinuity approach can guide future work to estimate potential minimum legal drinking age impacts on other health outcomes. (Am J Prev Med 2014;47(6):788–795) & 2014 American Journal of Preventive Medicine
Introduction
A
lcohol use is the largest contributor to the global burden of morbidity and mortality among adolescents and young adults.1,2 For many decades, countries worldwide have implemented minimum legal From the Northern Medical Program (Callaghan, Gatley), University of Northern British Columbia, Prince George, British Columbia; Human Brain Laboratory (Callaghan, Gatley), Centre for Addiction and Mental Health, Dalla Lana School of Public Health (Callaghan), University of Toronto; Biostatistical Consulting Unit (Sanches), Centre for Addiction and Mental Health, Toronto, Ontario; and the Department of Community Health and Epidemiology (Asbridge), Dalhousie University, Halifax, Nova Scotia, Canada Address correspondence to: Russell C. Callaghan, PhD, University of Northern British Columbia, Northern Medical Program, 3333 University Way, V2N 4Z9, Prince George British Columbia, Canada. E-mail: russ. [email protected]. 0749-3797/$36.00 http://dx.doi.org/10.1016/j.amepre.2014.08.012
788 Am J Prev Med 2014;47(6):788–795
drinking age (MLDA) legislation in order to reduce alcohol-related harms among young people.3 In the Canadian context, the MLDA is under provincial jurisdiction, and almost all provinces set their current legislated drinking ages in the mid-to-late 1970s. The MLDA is 18 years in Alberta, Manitoba, and Québec, and 19 years in the remainder of Canada. Recently, the Canadian Public Health Association4 and the Canadian National Alcohol Strategy working group5 have recommended raising the MLDA across all provinces to 19 years. In 2013, an expert panel alcohol-policy coalition identified a national MLDA of 21 years as the ideal,6 and province-specific recommendations have been released for all provinces (except Québec),7–15 endorsing an increase in the MLDA to 21 years. At their 2012 annual convention, the members of the Saskatchewan Party (the province’s conservative party) voted to lower the MLDA to 18 years, but this platform was later rejected by the
& 2014 American Journal of Preventive Medicine
Published by Elsevier Inc.
789
Callaghan et al / Am J Prev Med 2014;47(6):788–795 16
government. These Canadian MLDA discussions are occurring against broader movements in some jurisdictions to “modernize” alcohol policies so as to liberalize liquor access, shift to greater privatization of alcohol sales (away from a government monopoly model), and increase alcohol sales in the population.17–19 Current MLDA debates usually focus on a calculus of harms/benefits associated with proposed legislative changes, and motor vehicle collisions (MVCs) stand as one of the more prominent outcomes measured to assess the effectiveness of MLDA legislation. However, providing up-to-date estimates of the impacts of the MLDA on current patterns of MVCs represents a significant methodologic challenge. Most available studies assessing the impacts of MLDA legislation on MVCs have relied on naturalistic experiments occurring in the U.S. in the mid1980s,20 with few studies from other countries (e.g., New Zealand)21 or projects using data from other time periods. In general, the literature on the effects of MLDA changes on fatal/nonfatal MVCs in youth populations has found that raising the MLDA was associated with decreases, and lowering the MLDA was associated with increases.20,22–28 Many of these studies, however, are decades old and it would be reasonable to argue that the impacts of MLDA observed in the 1970s and 1980s might be substantially attenuated in the contemporary context, owing in large part to advances in both traffic safety and alcohol policy (e.g., road and vehicle safety,29,30 graduated driver licensing legislation,31–34 and impaired-driving laws35–37). This study makes an important contribution to Canadian4,6–8,16 and international38–41 (e.g., theamethys tinitiative.org/) MLDA debates by providing current estimates of MLDA effectiveness and demonstrating the use of a quasi-experimental statistical approach— regression-discontinuity (RD) analysis—for examining MLDA impacts on MVCs. RD analyses have been used previously to examine the impacts of U.S. MLDA laws on mortality42,43 and consumption of alcohol, cannabis, and tobacco.44,45 An RD approach does not rely on the occurrence of acute policy changes (i.e., natural experiments) to assess the impact of MLDA legislation on MVCs. The guiding hypothesis is that young adults slightly older than the MLDA would have significantly elevated collision patterns in comparison to those individuals still under the MLDA restrictions.
Methods Data Source De-identified data were obtained on police-reported MVCs occurring in Québec from January 1, 2000December 31, 2012 involving drivers aged 17.518.5 years from the Société de l'assurance automobile du Québec (SAAQ). The SAAQ is the sole December 2014
government insurer and insures against personal injury, while other private insurers provide coverage for property damage.46 The SAAQ MVC database captures all MVCs in the province reported to the SAAQ provincial insurance agency by the Québec police. Attending Québec police must report all collisions in the province to SAAQ in which a person sustained an injury. For MVCs causing property damage only, police must report to SAAQ all collisions in Québec if the property damage was estimated to be in excess of $1,000 before March 18, 2010 or $2,000 after that date. Off-road collisions (involving vehicles operating outside the Municipal, Provincial, or Federal road systems) are not included in the database. It is not possible to estimate the number of collisions unreported to SAAQ.
Analytic Plan An RD design47,48 was employed—a quasi-experimental approach that can provide credible estimates of the causal effect of an intervention on a specified outcome.49 The RD design takes advantage of the sharp discontinuity in the legality of alcohol purchasing and consumption appearing at the MLDA; this study’s approach assigns participants younger than the MLDA to the “alcohol-restricted” group and young adults no longer subject to the MLDA to the “alcohol-accessible” group. The primary, intuitive idea of the RD approach is that individuals slightly older and those slightly younger than the MLDA will be similar in observed (and unobserved) characteristics, except for the influence of the removal of the MLDA in the “alcohol-accessible” group. The RD design assumes that all observed and unobserved variables (which might influence the alcohol-related outcomes) are smoothly distributed across the age cutoff,50 and the effects of the MLDA can be inferred if the regression line shows a discontinuity—a change in intercept—at the MLDA.51 In other words, as the observed and unobserved determinants of the MVC outcomes (other than the legal granting of access to alcohol) are likely to be distributed smoothly across the MLDA threshold, any abrupt increases in the outcome rates immediately after the MLDA can be reasonably attributed to legal availability of alcohol. Additionally, a major advantage of the RD approach is that the results can be visually represented in easy-to-understand scatterplots. The mathematical formula (Equation 1) for the RD analyses is: P
Y¼ αþ β1 MLDAþ β2 Birth þ ∑ ðγk Agek þ λk Agek MLDAÞþ ε; k¼1
where the term Y is the number of MVCs; MLDA is the indicator of whether a driver’s age is above the MLDA of 18 years, and its coefficient β1 is the estimate of the MLDA effect; Birth is the indicator of birthday week (which accommodates “birthday celebration” effects occurring at the MLDA); Birth was coded as “1,” if the police-reported collision occurred during the individual’s birthday week), “0” for all other weeks; Age (in weeks) is a running variable, centered at the MLDA, with p¼1,2,3 representing the degree of the polynomial equation across Age, which includes the MLDAAge interaction term (the interaction allows for different regression equations before and after the MLDA cutoff); α is the intercept, which is the estimate of the baseline number of MVCs (i.e., the number of MVCs just before the legislated MLDA); and ε is the error term. The RD approach followed the recent best-practice guidelines for RD analyses.51 Parametric regression analyses were conducted, including linear, quadratic, and cubic models. Regarding selection
790
Callaghan et al / Am J Prev Med 2014;47(6):788–795
of the “best” model, the cubic model was chosen when the cubic term for age in Equation 1 was statistically significant; the quadratic model when the quadratic term for age was statistically significant (but not the cubic term); and a linear model when neither the cubic nor the quadratic term were statistically significant. In other words, the quadratic and cubic terms were tested in each full RD model, and then dropped from the final models if not statistically significant. The selection algorithm for the best model followed the standard rationale for model selection in regression analyses.52,53 Also, prior studies by this research team54–56 found significant gender-by-MLDA or gender-by-age interaction effects in all RD models—patterns that provide statistical justification for conducting gender-specific analyses. Sensitivity RD models were also run using Poisson regression, and these results confirmed our final findings (which were based on linear models). The RD models worked on aggregated MVC counts across age. Therefore, this approach does not follow individuals over time, but rather assesses population-based counts of driver involvement in MVCs across age groupings of age in weeks leading up to and after the MLDA across the data span. The R statistical package (“lm” and “glm”), version 2.15.3 was used to conduct the analyses. All data analyses were performed in 2013.
Results
Number of Drivers Involved in Collisions
Trends (centered at the MLDA) in the total number of MVCs for the combined sample, as well as for male and female drivers separately, can be found in Figure 1. Figure 1 demonstrates a significant and abrupt increase in MVCs occurring among youth slightly older than the MLDA for the total sample and male and female youth. Trends in the number of single-vehicle nighttime MVCs for the combined sample, as well as for male and female participants, can be found in Figure 2. The magnitude of the jumps at the MLDA can be found in the row “Effect (%)” in Tables 1 and 2. Among female youth, there was no evidence of a statistically significant increase in single-vehicle nighttime MVCs immediately after the MLDA. Among male youth, female youth, and the total sample, there was evidence of significant increases in all MVCs appearing immediately after the MLDA, with more pronounced “jumps” among male in comparison with female drivers. Tables 1 and 2 present key parameter results from linear RD models, which were the “best” fitting in all of the RD analyses (estimates for all RD parameters across Construction of Motor Vehicle Collision Outcomes all models [i.e., linear, quadratic, and cubic] are available from the primary author). Significant “jumps” were The SAAQ database does not include a variable indicating whether observed in total MVCs of 6.2% for the combined sample the MVC was alcohol-related. Therefore, the following proxies were used to identify alcohol-related MVCs: (1) nighttime MVCs (pr0.001), as well as for male (6.3%, p=0.003) and from the hours of 10:00PM to 6:59AM and (2) single-vehicle female (5.9%, p=0.047) youth (Figure 1). The number of nighttime MVCs. MVCs occurring at night are commonly used nighttime MVCs increased by 11.1% immediately after as a surrogate to identify alcohol-related collisions.3,36,57 Two the MLDA in the combined sample (p¼0.001), and thirds of fatal nighttime MVCs involve alcohol, compared with one increased by 9.5% among male drivers (p¼0.010). The quarter of daytime MVCs.43 number of daytime MVCs 1,600 increased by 5% among the Minimum legal drinking age combined sample (p¼0.003) 1,400 and by 5.5% among male youth (p¼0.012). The num1,200 ber of single-vehicle nighttime MVCs increased 9.3% Total for the total sample 1,000 (p¼0.006) and 8.7% among Female male drivers (p¼0.990) 800 Male (Figure 2). There were also nonsignificant increases 600 among female drivers of 16.3% in the number of 400 nighttime MVCs (p¼0.060), 4.2% in the number of day200 time MVCs (p¼0.191), and 13.1% in the number of 0 single-vehicle nighttime 18.5 18 17.5 MVCs (p¼0.328) (Figure 2). Drivers' Age in Years Visual and statistical tests (BreuschPagan) were perFigure 1. Police-reported motor vehicle collisions among individuals aged 17.518.5 formed on the presented final years in Québec, 20002012. www.ajpmonline.org
791
Callaghan et al / Am J Prev Med 2014;47(6):788–795
MVCs were evaluated at ages 17 and 19 years, and there was no evidence of statistically significant discontinuities (data not shown, available from first author).
180 Number of Drivers Involved in Collisions
Minimum legal drinking age 160 140 120 100
Total Female
Discussion
MLDA legislation has a powerful impact on MVCs among 60 young drivers in Québec, Canada. In comparison to youth just 40 younger than the MLDA, male and female youth just older than 20 the MLDA had a significant increase of approximately 6% 0 in population-level MVCs, as 17.5 18 18.5 well as an 11% increase in the Drivers' Age in Years number of nighttime MVCs. Granting that the major assumpFigure 2. Police-reported single-vehicle nighttime (10:00PM to 6:59AM) motor vehicle tions of the analytic approach collisions among individuals aged 17.518.5 years in Québec, 20002012. (RD) were met, this study can RD models to ensure homoscedasticity of variance in the provide credible population-based estimates of the causal residuals. No violations appeared. RD models using impact of granting legal access to alcohol on the number Poisson regression showed results similar to the final of MVCs among young people in Québec. presented models (data not shown). The estimates of the impacts of the MLDA on MVCs Based on these results, estimates were also made that dovetail with findings from the existing, albeit older, raising the MLDA to 19 years in Québec would reduce MLDA literature, which is primarily from the U.S. the number of MVCs involving at least one 18-year-old Raising the U.S. MLDA to 21 years (from ages 18 or 19 driver by 6.2%, resulting in 4,376 fewer collisions years, depending on jurisdiction) was associated with (6.2% 70,585 MVCs involving at least one 18-year-old decreases (1%8%58 and 8%17%22) in alcohol-related driver) from 2000 to 2012. It was estimated that raising fatal/nonfatal MVCs among drivers aged 1820 years, the MLDA to 19 years would result in approximately 337 and an 11% decrease in the proportion of alcohol-related fewer collisions per year (4,376 total collisions/13-year fatal MVCs for the whole population59; lowering of the data span) involving at least one 18-year-old driver in MLDA was associated with an increase in the total Québec. Assuming a reduction of the MLDA effect by number of fatal MVCs among 18- to 21-year-olds by half for each year of age after 18 years (i.e., 6.2% for 187%9% (Carpenter C, Dobkin C. The effects of the year-olds, 3.1% for 19-year-olds, and 1.55% for 20-yearminimum legal drinking age on morbidity, unpublished olds), it could be expected that such a policy would result observations, 2011).24 In relation to nighttime/singlein approximately 7,578 fewer MVCs during the 13-year vehicle nighttime MVCs, evidence suggests that lowering study period (6.2% 70,585 ¼ 4376 MVCs involving at the MLDA from 21 to 18 years was associated with a 17% least one 18-year-old driver, 3.1% 70,006 ¼ 2,170 increase in fatal nighttime (8:00PM to 5:59AM) MVCs MVCs involving at least one 19-year-old driver, and among 18- to 20-year-olds (Carpenter C, Dobkin C. The 1.55% 66,597 ¼ 1032 MVCs involving at least one 20effects of the minimum legal drinking age on morbidity, year-old driver, 4376 þ 2170 þ 1032 ¼ 7,578). If the unpublished observations, 2011). As a result, this study MLDA were raised to 21 years in Québec, it was not only shows the usefulness of the RD approach for estimated that this would prevent approximately 583 recovering reasonable estimates of the impacts of MLDA police-reported MVCs per year involving at least one legislation, but also demonstrates the continuing effecdriver aged between 18 and 20 years. tiveness of MLDA laws as an integral component in the 51 Guidelines for the use of RD analyses suggest testing contemporary array of alcohol-control and drivingfor jumps at nearby nondiscontinuity points before and related policies designed to reduce MVCs among youth after the specified forcing variable (the MLDA). Jumps in in the population. 80
December 2014
Male
792
0.1900 0.0119
4.2 (2.1, 10.5) 5.5 (1.3, 9.7)
Note: Boldface indicates statistical significance (po0.05). a The Québec MLDA is 18 years of age. b Percentage change in MVC events at the MLDA threshold (the coefficient of the MLDA indicator divided by the intercept of the model). MLDA, minimum legal drinking age; MVC, motor vehicle collision; RD, regression-discontinuity.
0.0034 0.0473 0.0031 MLDA effect, p-value
0.0004
5.9 (0.1, 11.8) Effect (%)
6.2 (2.9, 9.4)
6.3 (2.2, 10.4)
5 (1.8, 8.3)
0.9 (2.5, 0.6) 0.7 (2.5, 1.1) 0.6 (2.3, 1.1)
b
Age MLDA
1.7 (4.4, 1.1)
1.1 (3.3, 1.2)
1.7 (3.9, 0.6)
25.3 (70.1, 19.4) 1.6 (50.1, 53.3) 33.7 (82.2, 14.8) Birthday week
52.2 (129.6, 25.3)
16.9 (80.3, 46.5)
25 (88.6, 38.6)
15.8 (8.1, 39.6) 35.9 (8.3, 63.4) 26.2 (0.3, 52.1) MLDA
78.7 (37.4, 120.1)
52.46 (18.6, 86.3)
52.1 (18.1, 86.0)
0.8 (0.3, 1.8) 1.6 (0.4, 2.9) 0.7 (0.5, 1.9)
2.4 (0.9, 3.9)
Although the results of this study cannot directly answer the counterfactual question—How many MVCs would be prevented if the Québec MLDA were raised to 19 years?—these findings can provide a reasonable estimate. It was estimated that raising the Québec MLDA to 19 years would prevent 337 police-reported collisions per year involving at least one 18-year-old driver in the province. If the MLDA were to be raised to 21 years, it could be expected that this legislation would result in the prevention of approximately 583 police-reported MVCs per year involving at least one driver aged between 18 and 20 years.
Legislative Changes Related to Driving in Québec, 20002012
2.64 (1.1, 4.2) 3.3 (1.5, 5.2) Age
377.6 (360.9, 394.3) 652.5 (633.2, 671.8) 441.5 (423.4, 459.6) Intercept
1272.4 (1243.5, 1301.3)
828.4 (804.7, 852.1)
1032 (1008.2, 1055.7)
Female (95% CI) Male (95% CI) Total (95% CI) Female (95% CI) Male (95% CI) Total (95% CI) Model parameters
All MVCs
Table 1. RD parameters: drivers involved in all and daytime MVCs following the Québec MLDAa, 20002012
Daytime MVCs (7:00AM9:59PM)
Callaghan et al / Am J Prev Med 2014;47(6):788–795
During the span of this study, several pieces of legislation affecting young/new drivers were enacted in Québec, however, it is unlikely that any of these would have impacted our estimates. The following laws were implemented in Québec between 2000 and 2012: harsher penalties for impaired driving and speeding (April and December 2008),60 mandatory completion of an approved Road Safety Education Program to obtain a learner’s license (January 17, 2010),61 a graduated demerit point scale for drivers younger than age 25 years (June 19, 2011),62 and a zero-tolerance blood alcohol concentration law was introduced for drivers aged r21 years and for those drivers with a learner’s or probationary license (April 15, 2012),63 It was not expected that these changes would confound the estimates of the impacts of the MLDA legislation on MVCs because the legislation did not differentially affect those drivers slightly younger and those just older than the MLDA of 18 years.
Limitations The findings of the current study must be interpreted in light of a number of limitations. The analytic strategy employed an RD approach, which assumes that potentially confounding variables are smoothly distributed across the MLDA cutoff. If a factor differentially affected individuals on either side of the MLDA, then this would undermine the validity of the estimates. In Québec, there is a major educational transition from high school to a 2- or 3-year post-secondary Collège d'enseignement général et professionnel (CÉGEP) program, typically entered at age 17 years.64,65 In the analyses, drivers aged 17.518.5 years were included. This span does not overlap with major transitions into or out of the CÉGEP system, limiting the possibility that educational transitions may have affected the outcomes. In addition, the outcomes only included police-reported MVCs in www.ajpmonline.org
December 2014
Note: Boldface indicated statistical significance (po0.05). a The Québec MLDA is 18 years of age. b Percentage change in MVC events at the MLDA threshold (the coefficient of the MLDA indicator divided by the intercept of the model). MLDA, minimum legal drinking age; MVC, motor vehicle collision; RD, regression-discontinuity.
0.3300 0.9900 0.0600 MLDA effect, p-value
0.0013
0.0102
0.0060
13.1 (13.2, 39.4) 8.7 (11.8, 11.9) 16.3 (1.7, 34.3) 9.5 (2.2, 16.7) Effect (%)
11.1 (4.3, 17.7)
9.3 (2.7, 16.0)
0.7 (0.2, 1.1) 0.1 (0.8, 0.6) 0.3 (0.4, 1.1) 0.4 (1.2, 0.5)
b
Age MLDA
0.0 (1.0, 1.0)
0.5 (0.2, 1.2)
3.3 (9.2, 15.7) 2.5 (16.2, 21.3) 8.4 (28.8, 12.1) 18.5 (41.9, 4.9) Birthday week
27.1 (56.4, 2.2)
5.7 (14.0, 25.3)
3.5 (3.2, 10.1) 7.5 (2.5, 17.5) 10.4 (0.5, 21.3) 16.6 (4.1, 29.1) MLDA
26.7 (11.0, 42.3)
10.5 (0.1, 21.0)
0.3 (0.6, 0.0) 0.5 (0.0, 0.9) 0.1 (0.6, 0.4) Age
0.9 (0.2, 1.7)
1 (0.4, 1.6)
0.2 (0.3, 0.7)
26.3 (21.6, 30.9) 86 (79.0, 93.0) 63.9 (56.3, 71.6) 175.9 (167.1, 184.6) Intercept
240.5 (229.5, 251.4)
112.8 (105.5, 120.1)
Female (95% CI) Male (95% CI) Total (95% CI) Female (95% CI) Male (95% CI) Total (95% CI) Model parameters
Single-vehicle nighttime MVCs (10:00PM to 6:59AM) Nighttime MVCs (10:00PM to 6:59AM)
Table 2. RD parameters: drivers involved in nighttime and single-vehicle nighttime MVCs following the Québec MLDA,a 20002012
Callaghan et al / Am J Prev Med 2014;47(6):788–795
793
Québec, and it was not possible to estimate the number of unreported MVCs during the data span. Nonetheless, if alcohol-related MVCs are more likely to go unreported than other MVCs, then the estimates of the impacts of the MLDA MVCs using SAAQ data would be conservative. Unfortunately, the data did not include information about driving experience (or age of initial licensing). However, it is reasonable to expect that older individuals included in the analyses would have more driving experience. If increased driving experience in this population confers a reduced risk of MVC, it is likely that the estimated effect of the MLDA is conservative, given the findings of elevated MVC patterns in the moreexperienced young drivers in the post-MLDA age group. Also, in calculations of the potential MVCs prevented if the MLDA were in Québec, it was assumed that there would be a 50% reduction in the demonstrated effect of the MLDA for each year of age after 18 years (i.e., 6.2% for 18-year-olds, 3.1% for 19-year-olds, and 1.55% for 20year-olds). The actual impacts of the MLDA on 19- to 20year-olds may be different.
Conclusions Given the very recent recommendations to raise the Canadian MLDA to 19 years (or to 21 years in some provinces), it is critical for Canadian alcohol policy debates to have current estimates of the impacts of the MLDA on MVCs—a key public health outcome. The available Canadian research on the effects of the MLDA on MVCs was published from the period from 1975 to 1981 and, therefore, this study provides important up-todate information demonstrating that MLDA legislation continues to have a significant impact on MVCs among male and female youth. The authors would like to thank Julie Béliveau (Statistician [Direction des études et des stratégies en sécurité routière, Société de l'assurance automobile du Québec]) for her assistance in helping us to acquire the Québec collision database and understand its structure. The current study was supported through internal startup funds from the Northern Medical Program (University of Northern British Columbia) to the first author (RCC). No financial disclosures were reported by the authors of this paper.
References 1. Gore FM, Bloem PJ, Patton GC, et al. Global burden of disease in young people aged 1024 years: a systematic analysis. Lancet 2011; 377(9783):2093–102. 2. Lim SS, Vos T, Flaxman AD, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk
794
3. 4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18. 19.
Callaghan et al / Am J Prev Med 2014;47(6):788–795
factor clusters in 21 regions, 19902010: a systematic analysis for the global burden of disease study 2010. Lancet 2012;380(9859):2224–60. Babor T, Caetano R, Casswell S, et al. Alcohol: no ordinary commodity. 2nd ed. New York NY: Oxford University Press, 2010. Canadian Public Health Association. Canadian Public Health Association position paper: too high a cost: a public health approach to alcohol policy in Canada. Ottawa ON: Canadian Public Health Association, 2011 www.cpha.ca/uploads/positions/position-paper-alco hol_e.pdf. Sawka E, Liepold H, Lockhart N, Song S, Thomas G. Reducing alcoholrelated harm in Canada: toward a culture of moderation. Recommendations for a national alcohol strategy. Ottawa ON: Canadian Centre on Substance Abuse, 2007 www.ndphs.org///documents/515/Canada_ Paper_NAS_to_Riga_Conference_Jan_30_07_1.pdf. Giesbrecht N, Wettlaufer A, April N, Asbridge M, et al. Strategies to reduce alcohol-related harms and costs in Canada: a comparison of provincial policies. Toronto ON: Centre for Addiction and Mental Health, 2013. www.camh.ca/en/research/news_and_publications/reports_and_ books/Documents/Strategies%20to%20Reduce%20Alcohol%20Related% 20Harms%20and%20Costs%202013.pdf. Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Ontario: a provincial summary report. Toronto ON: Centre for Addiction and Mental Health, 2013 www.camh.ca/en/research/Docu ments/Provincial%20summary_ON_final.pdf. Thompson K, Stockwell T, Vallance K, Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in British Columbia: a provincial summary report. CARBC Bulletin #10. Victoria BC: Centre for Addictions Research of British Columbia, 2013 www.carbc.ca/ Portals/0/propertyagent/558/files/335/bulletin%202013-08.pdf. Vallance K, Thompson K, Stockwell T, Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Alberta: a provincial summary report. Victoria BC: Centre for Addictions Research of BC, 2013. www.carbc.ca/Portals/0/propertyagent/558/files/352/albertaprov summ2013-09.pdf. Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Manitoba: a provincial summary report. Toronto ON: Centre for Addiction and Mental Health, 2013. Giesbrecht N, Wettlaufer A. Reducing alcohol-related harms and costs in Saskatchewan: a provincial summary report. Toronto ON: Centre for Addiction and Mental Health, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in New Brunswick: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in Newfoundland and Labrador: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in Nova Scotia: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. Asbridge M, Pauley C. Reducing alcohol-related harms and costs in Prince Edward Island: a provincial summary report. Halifax NS: Department of Community Health and Epidemiology, Dalhousie University, 2013. CBC News. Drinking age will remain 19 in Saskatchewan. CBC News. 2013. www.cbc.ca/news/canada/saskatchewan/story/2013/03/04/skdrinking-age-1303.html. British Columbia Ministry of Justice. B.C. liquor policy review final report. Victoria BC: British Columbia Ministry of Justice, 2013. www2. gov.bc.ca/local/haveyoursay/Docs/liquor_policy_review_report.pdf. Government of Saskatchewan. Liquor regulatory review—additional information. Regina SK: Government of Saskatchewan, 2013. Liquor and Gaming Regulatory Consultation Committee. A discussion paper on liquor and gaming regulation. Winnipeg MB: Manitoba Gaming Control Commission, 2012.
20. Wagenaar AC, Toomey TL. Effects of minimum drinking age laws: review and analyses of the literature from 1960 to 2000. J Stud Alcohol Suppl 2002;14:206–25. 21. Kypri K, Voas RB, Langley JD, et al. Minimum purchasing age for alcohol and traffic crash injuries among 15- to 19-year-olds in New Zealand. Am J Public Health 2006;96(1):126–31. 22. Shults RA, Elder RW, Sleet DA, et al. Reviews of evidence regarding interventions to reduce alcohol-impaired driving. Am J Prev Med 2001;21(4S):66–88. 23. McCartt AT, Hellinga LA, Kirley BB. The effects of minimum legal drinking age 21 laws on alcohol-related driving in the United States. J Safety Res 2010;41(2):173–81. 24. Cook PJ. Paying the tab: the costs and benefits of alcohol control. Princeton NJ: Princeton University Press, 2007. 25. Fell JC, Fisher DA, Voas RB, Blackman K, Tippetts AS. The impact of underage drinking laws on alcohol-related fatal crashes of young drivers. Alcohol Clin Exp Res 2009;33(7):1208–19. 26. Fell JC, Fisher DA, Voas RB, Blackman K, Tippetts AS. The relationship of underage drinking laws to reductions in drinking drivers in fatal crashes in the United States. Accid Anal Prev 2008;40(4):1430–40. 27. Voas RB, Tippetts AS, Fell JC. Assessing the effectiveness of minimum legal drinking age and zero tolerance laws in the United States. Accid Anal Prev 2003;35(4):579–87. 28. Ponicki WR, Gruenewald PJ, LaScala EA. Joint impacts of minimum legal drinking age and beer taxes on US youth traffic fatalities, 1975 to 2001. Alcohol Clin Exp Res 2007;31(5):804–13. 29. Kahane CJ. Lives saved by the federal motor vehicle safety standards and other vehicle safety technologies, 1960-2002—passenger cars and light trucks—with a review of 19 FMVSS and their effectiveness in reducing fatalities, injuries and crashes. Washington DC: Evaluation Division, National Center for Statistics and Analysis National Highway Traffic Safety Administration, 2004. 30. Waller PF. Challenges in motor vehicle safety. Annu Rev Publ Health 2002;23:93–113. 31. Dee TS, Grabowski DC, Morrisey MA. Graduated driver licensing and teen traffic fatalities. J Health Econ 2005;24(3):571–89. 32. McCartt AT, Teoh ER, Fields M, Braitman KA, Hellinga LA. Graduated licensing laws and fatal crashes of teenage drivers: a national study. Traffic Inj Prev 2010;11(3):240–8. 33. Masten SV, Foss RD, Marshall SW. Graduated driver licensing and fatal crashes involving 16- to 19-year-old drivers. JAMA 2011;306(10): 1098–103. 34. Mayhew DR, Simpson HM, Singhal D. Best practices for graduated driver licensing in Canada. Ottawa ON: Traffic Injury Research Foundation, 2005 www.ibc.ca/en/Car_Insurance/documents/gradua ted_licensing/TIRF-fullreportGDL-oct2005.pdf. 35. Asbridge M, Mann RE, Smart RG, et al. The effects of Ontario’s administrative driver's license suspension law on total driver fatalities: a multiple time series analysis. Drugs Educ Prev Policy 2009;16(2): 140–51. 36. Mann RE, Macdonald S, Stoduto G, Bondy S, Jonah B, Shaikh A. The effects of introducing or lowering legal per se blood alcohol limits for driving: an international review. Accid Anal Prev 2001;33(5):569–83. 37. Vingilis E, Blefgen H, Lei H, Sykora K, Mann R. An evaluation of the deterrent impact of Ontario’s 12-hour license suspension law. Accid Anal Prev 1988;20(1):9–17. 38. Cobiac L, Vos T, Doran C, Wallace A. Cost-effectiveness of interventions to prevent alcohol-related disease and injury in Australia. Addiction 2009;104(10):1646–55. 39. Doran CM, Hall WD, Shakeshaft AP, Vos T, Cobiac LJ. Alcohol policy reform in Australia: what can we learn from the evidence? Med J Aust 2010;192(8):468–70. 40. Manins R. Alcohol reform bill through faster. Otago NZ: Otago Daily Times, 2012 www.odt.co.nz/news/dunedin/237188/alcohol-reformbill-through-faster.
www.ajpmonline.org
Callaghan et al / Am J Prev Med 2014;47(6):788–795 41. Toomey TL, Nelson TF, Lenk KM. The age-21 minimum legal drinking age: a case study linking past and current debates. Addiction 2009;104(12):1958–65. 42. Carpenter C, Dobkin C. The effect of alcohol consumption on mortality: regression discontinuity evidence from the minimum drinking age. Am Econ J Appl Econ 2009;1(1):164–82. 43. Carpenter C, Dobkin C. The minimum legal drinking age and public health. J Econ Perspect 2011;25(2):133–56. 44. Yörük BK, Yörük CE. The impact of minimum legal drinking age laws on alcohol consumption, smoking, and marijuana use: evidence from a regression discontinuity design using exact date of birth. J Health Econ 2011;30(4):740–52. 45. Yörük CE, Yörük BK. The impact of drinking on psychological wellbeing: evidence from minimum drinking age laws in the United States. Soc Sci Med 2012;75(10):1844–54. 46. Insurance Bureau of Canada. Car insurance. http://www.ibc.ca/en/ Car_Insurance/PQ/. 47. Shadish WR, Cook TD, Campbell DT. Experimental and quasiexperimental designs for generalized causal inference. Boston MA: Houghton Mifflin Company, 2002. 48. Thistlethwaite DL, Campbell DT. Regression-discontinuity analysis: an alternative to the ex post facto experiment. J Educ Psychol 1960;51(6): 309–17. 49. Lee DS, Lemieux T. Regression discontinuity designs in economics. J Econ Lit 2009;48(2):281–355. 50. Hahn J, Todd P, Van der Klaauw W. Identification and estimation of treatment effects with a regression-discontinuity design. Econometrica 2001;69(1):201–9. 51. Imbens GW, Lemieux T. Regression discontinuity designs: a guide to practice. J Econometrics 2007;142(2):615–35. 52. Seber GA, Lee AJ. Linear regression analysis. New York NY: John Wiley & Sons Inc, 2003. 53. Freund RJ, Wilson WJ, Sa P. Regression analysis: statistical modeling of a response variable. 2nd ed. New York NY: Academic Press by Elsevier Inc, 2006. 54. Callaghan RC, Sanches M, Gatley JM, Cunningham JK. Effects of the minimum legal drinking age on alcohol-related health service use in hospital settings in Ontario: a regression-discontinuity approach. Am J Public Health 2013;103(12):2284–91.
December 2014
795
55. Callaghan RC, Sanches M, Gatley JM. Impacts of drinking-age laws on mortality in Canada, 1980–2009. Drug Alcohol Depen 2014;138: 137–45. http://dx.doi.org/10.1016/j.drugalcdep.2014.02.019. 56. Callaghan RC, Sanches M, Gatley JM. Impacts of the minimum legal drinking age legislation on in-patient morbidity in Canada, 19972007: a regression-discontinuity approach. Addiction 2013;108(9):1590–600. 57. Young DJ, Stockwell T, Cherpitel CJ, et al. Emergency room injury presentations as an indicator of alcohol-related problems in the community: a multilevel analysis of an international study. J Stud Alcohol 2004;65(5):605–12. 58. Hoskin A, Yalung-Mathews D, Carraro B. The effect of raising the legal minimum drinking age on fatal crashes in 10 states. J Safety Res 1986;17:117–21. 59. Chang K, Wu CC, Ying YH. The effectiveness of alcohol control policies on alcohol-related traffic fatalities in the United States. Accid Anal Prev 2012;45:406–15. 60. Berthod C, Audet L, Bélanger C. Table Québécoise de la sécurité routière [Quebec safety task force]. Table Québécoise de la sécurité routière [Quebec safety task force]. Presentation for “Road safety vision successor plan for 2015 and other safety plans” at the Transportation Association of Canada’s 2010 Annual Conference and Exhibition in Halifax, NS, 2010. http://conf.tac-atc.ca/english/resourcecentre/read ingroom/conference/conf2010/docs/c1/berthod-e.pdf. 61. Société de l'assurance automobile du Québec. Frequently asked questions. Mandatory driving course measures in effect as of January 17, 2010. www.saaq.gouv.qc.ca/en/faq/driving_course.php#q1. 62. Société de l'assurance automobile du Québec. Driver's licence. Penalties related to demerit points. www.saaq.gouv.qc.ca/en/driver_licence/pen alties_demerit_points.php. 63. Société de l'assurance automobile du Québec. Road safety. Zero alcohol. www.saaq.gouv.qc.ca/en/road_safety/behaviour/alcohol/laws_ penalties_costs/zero_alcohol.php. 64. Statistics Canada. Table 1. Postsecondary participation rates of young adults aged 24 to 26 by December 2005, by province and type of institution attended. Toronto ON: Statistics Canada, 2008. www. statcan.gc.ca.myaccess.library.utoronto.ca/pub/81-595–m/2008070/t/ 6000006-eng.htm. 65. Les CÉGEPS du Québec. Directory of programs. http://www.cegep squebec.ca/en/study-in-quebec/programs/.
